Reliability of Visual Field Index in Staging Glaucomatous Visual Field Damage NC05-NC08
Dr. Neetha Kuzhuppilly
Assistant Professor, Department of Ophthalmology, Kasturba Medical College, Manipal, Udupi, Karnataka, India.
Introduction: Standard automated perimetry is integral to the testing of visual function in glaucoma. Classification of glaucomatous visual field defects into different severity levels is important to guide effective management; but the available classification systems may be cumbersome and impractical on a daily basis.
Aim: To quantify, correlate and analyse the relation between Visual Field Index (VFI) and the stages of glaucomatous field damage as defined by Hodapp Parrish Anderson (HPA). To check the validity of Glaucoma Staging Indices (GSI), which is a new glaucomatous field classification system dependent on VFI.
Materials and Methods: The study was a prospective, observational analysis of consecutive visual field tests done between August 2015 and March 2016. The Institutional Ethical Committee approved the protocol, and participants who gave written informed consent were included in the study. Patients underwent a comprehensive eye examination including standard automated perimetry with Humphrey Visual Field Analyser. Data was collected from each visual field and the fields were evaluated and classified into four stages- Normal, Early defect, Moderate defect or Severe defect based on HPA classification. HPA and Geological Strength Index (GSI) classification systems were compared and analysed with Kappa analysis.
Results: Analysis of 170 visual fields of 95 patients showed that VFI was significantly different between Normal, Early defect, Moderate defect and Severe defects as classified with HPA staging, p<0.001. VFI had strong positive correlation with Mean Deviation (MD), r=0.984, p<0.001 and non-linear correlation with Pattern Standard Deviation (PSD), r = -0.472, p<0.001. On comparing HPA staging with GSI, ?=0.633, p<0.001. VFI, MD and PSD in each of the severity stages across the two classification systems showed no significant differences (p>0.05).
Conclusion: In established glaucoma, GSI is a good dependable staging system. It is readily available on the single field print out and can be a quick reference for decision making in the management of glaucoma patients.